There are many parameters that characterize semiconductor materials and devices. For example, semiconductor materials are characterized by parameters such as the energy bandgap, the carrier mobilities, and the carrier effective masses. Semiconductor devices having, for example, a p-n junction, are characterized by parameters such as the depletion region width and capacitance as well as current-voltage characteristics. Accordingly, techniques for measuring these parameters are of interest and have been devised.
One area of interest for semiconductor devices is the measurement of the current-voltage characteristics at a p-n junction. This is of special interest for laser diodes for which the forward current determines the light output. For several reasons, for example, reduction of cross-section area to reduce operating current, improved reliability by removing the junction perimeter from the surface, and elimination of multifilament lasing, it is desirable to fabricate lasers having a narrow active region. In such lasers, the active region is in the form of a stripe. Measurements that would permit mapping of the current distribution for a p-n junction would be desirable as they would enable the amount of current confinement to be ascertained. However, it has hitherto been difficult to map the forward current distribution for p-n junctions in semiconductor laser diodes.